I'm using CentOS 5.5 with smbclient 3.0.33-3.28-el5 (latest version in repo), and I can't overwrite files in my Samba store.

I am not the admin for the Samba server, so there isn't anything I can do server side. But I do have write permission to the server. I know the server runs Windows XP or Server 2003; I don't know.
I can delete the file, and then copy the new version over, but I can't overwrite it.

Using the cp command I'll get this error:

[jonescb@localhost ~]$ cp foo.txt /mnt/si_storage/foo.txt
cp: cannot create regular file `/mnt/si_storage/foo.txt': No such file or directory`

And if I edit a file on the server using vim, I can save it once, but if I save it again I get this:
"/mnt/si_storage/foo.txt" E212: Can't open file for writing

This is my /etc/fstab entry for the samba server:
//192.168.1.2/SI_STORAGE /mnt/si_storage cifs username=myuser,password=mypass 0 0

Edit: I can overwrite files just fine on my XP machine. The CentOS box is the only one having problems.